The invention relates to a base plate for at least one carbon brush, comprising a carbon brush guide that extends outward from the base plate, a spring element via which the carbon bush can be pushed in the direction of a commutator or slip ring, and a retaining element that serve to hold the carbon brush back against the force generated by the spring element.
One known-in-the-art brush holder is disclosed in EP 0 236 254 B1, in which a disc-shaped retaining element is connected via breakable tabs to carbon brush tubes, allowing the brush holder to be pushed back into an armature shaft with a commutator, without the carbon brushes getting in the way. In its mounted position, then, by breaking the tabs, the retaining element can be removed, allowing the carbon brushes to become engaged against the commutator by the force of a spring. A similar retaining element is used with a brush holder in U.S. Pat. No. 4,293,789, however in this case the retaining element is not connected to the carbon brush tubes or guides. In DE-GM 84 27 601, a hammer brush holder system for a commutator motor is described, in which the brush holder is connected via a course-disrupting crosspiece, which allows the carbon brushes, which extend outward from the brush holders, to act on the commutator via spring force.
The retaining elements used in the known-in-the-art brush holders or base plates always require two carbon holders to maintain the carbon brushes, which are mounted such that they can shift in the retaining elements, in their retracted position during assembly. Furthermore, with the exception of the hammer brush-holder system, the retaining elements extend outward from the ends of the carbon brush holders, which can cause interference during assembly.
The object of the present invention is to develop an improvement on a base plate of the type described above, such that with simple design alterations it will be possible to maintain a carbon brush in its retracted position during assembly, without this in itself causing interference during assembly. It should further be possible to align the retaining element specifically with one carbon brush, without requiring several carbon brush guides at the same time.
The object is essentially attained in accordance with the invention in that the retaining element is mounted in the base plate such that it can be shifted, and such that when the carbon brush is retracted, the retaining element is engaged in a recess in the base plate.
In contrast to the current state of the art, the carbon brush is not attached to an adjacent retaining element, rather it is attached via a retaining element that becomes engaged in the carbon brush itself. This allows the end area of the carbon brush to be completely free, thus excluding interference during assembly. More importantly, it also makes it possible to retract the carbon brush completely into the carbon brush guide, as the recess may be positioned at the back of the carbon brush, for example, with a retaining element that also is positioned at the back.
In a further development of the invention, the base plate, which may be cupular or pot-shaped, can be covered with an element which, when the base plate is covered, causes the retaining element to become disengaged from the carbon brush. This element may be a cap or ring-shaped element, but is preferably an element that is connected to a motor frame, such as a centering element or border.
A further proposal provides for the retaining element to be positioned in a base plate guide that runs perpendicular or essentially perpendicular to the lengthwise axis of the carbon brush, such that the retaining element can be shifted in this guide, and can be braced against this guide via a spring element. In this manner, the retaining element can be forced in the direction of the carbon brush via the spring element. Alternatively, the retaining element can be wedged via an automatic self-locking device.
The retaining element itself is equipped with a pin-or cylinder-shaped extension on its side that faces the carbon brush, which, when the carbon brush is retracted, becomes engaged in the recess in the manner of a pocket hole.
The retaining element is equipped with a section that extends along a wall that extends outward from the bottom of the base plate and runs around the circumference of the base plate, and that is preferably rectangular in its cross-section; this first section graduates to a center section that run perpendicular to the first, and from which extend the pin-shaped extension, and, on its opposite side, a second section that is positioned in the guide that extends outward from the bottom.
The guide can be formed by two parallel, bar-shaped partitions, wherein, the spring element is positioned inside the guide, between the second section of the retaining element and the bottom of the base plate.
In a more novel embodiment of the invention, the carbon brush guide can comprise a U-shaped metal element, with knee-angled sections that run parallel to the bottom of the base plate, or parallel to the partitions in the base plate which run parallel to the bottom of the base plate, wherein the cross-section of the area surrounded by the U-shaped section of the metal element corresponds to that of the carbon brush. Alternatively, this section may penetrate directly through the base plate, in other words without the sections that extend parallel to the base plate.
The ends of the knee-angled sections of the U-shaped metal element may also extend through the partition.
It is preferably provided, however, that in order to form the U-shape, the carbon brush guide may be comprised of a first section that extends along the opposite side walls and the end wall of the carbon brush, and a second section that extends outward from the side legs of the first section, wherein the legs of the second section extend, at least in part, parallel to the bottom or the partition of the base plate. In addition, each leg of the second section may comprise a first leg section that extends along the bottom or the partition, and a second, outer leg section that extends through the bottom or the partition.
A further development of the invention provides for a plate-shaped metal element to extend between the carbon brush and the bottom or the partition wall, along which the carbon brush can slide, with this plate-shaped element being connected to the U-shaped metal element and/or penetrated by its second section. In this, the free ends of the legs of the U-shaped metal element that extend through the base or partition wall can be bent around, bent at right angles, or otherwise secured in order to attach or mount the legs to the surface of the bottom or the side wall that lies opposite the carbon brush.
In particular, the invention provides for an automatic release of the retaining element when the base plate is covered with the covering element, since the first section of the retaining element juts out over the edge of the base plate in the carbon brush holding position, and when the base plate is closed it is pushed back against the spring force that is acting against the retaining element, to such an extent that the cylinder or pin-shaped section becomes disengaged from the carbon brush, causing the brush to be shifted via the force of the spring in the carbon brush guide, in the direction of the commutator or slip ring.
The base plate specified in the invention is particularly well suited for use in motors in which an exchange of carbon brushes is not required, for example sporting devices such as treadmills, golf carts, etc. There are no limitations to its use in other applications, however, since a design that complies with the teaching of the invention can be used in a multitude of ways.
Because the retaining element can be shifted perpendicular to the lengthwise axis of the carbon brush, and especially because it can become engaged at the back, the end area of the carbon brush in the recess that is located there, in the manner of a pocket hole, a problem-free assembly of the carbon brush guide with carbon brushes can take place, without any interference by the retaining element such as is caused with known-in-the-art disc-type elements that are mounted at the end of the carbon brush guide.